Round according to nearest decimal value - java

Question

I have used this one

Math.round(input * 100.0) / 100.0;

but it didn't work with my requirement. I want to round into two decimal points according to nearest decimal value.

firstly I want to check fourth decimal value if it is 5 or above I want to add 1 into 3rd decimal value then want to check 3rd one if it is 5 or above I want to add 1 into 2nd one

ex: if I have 22.3246

refer above example number. 4th decimal no is 6. we can add 1 into 3rd decimal value.

result : 22.325

now 3rd decimal no is 5. we can add 1 into 2nd decimal value

result : 22.33

I want to get result 22.33

Are you aware that your desired result, 22.33 is (in terms of distance to the original value) worse than the standard rounding result of 22.32? — Ralf Kleberhoff, Jan 06 '21 at 10:05
@RalfKleberhoff ya I know that. but this is the requirement. — max, Jan 06 '21 at 13:25

score 3 · Accepted Answer · answered Jan 06 '21 at 09:53

3

If you want to respect the 4th decimal digit, you can do it in this way:

double val = Math.round(22.3246 * 1000.0) / 1000.0;
double result = Math.round(val * 100.0) / 100.0;
System.out.println(result); // print: 22.33

answered Jan 06 '21 at 09:53

dyon048

174
4

score 0 · Answer 2 · answered Jan 06 '21 at 10:00

You can use BigDecimal class to accomplish this task, in combination with a scale and RoundingMode.HALF_UP.

Sample code:

System.out.println(new BigDecimal("22.3246").divide(BigDecimal.ONE,3,RoundingMode.HALF_UP)
                    .divide(BigDecimal.ONE,2,RoundingMode.HALF_UP));

Output:

22.33

score 0 · Answer 3 · answered Jan 07 '21 at 10:56

According to your requirement, the greatest number to be rounded down to 22.32 is 22.3244444444.... From 22.32444...4445 on, iteratively rounding digit per digit will lead to 22.33.

So, you can add a bias of 0.005 - 0.0044444444 (standard rounding threshold minus your threshold), being 5/9000 and then round to the next 1/100 the standard way:

    double BIAS = 5.0 / 9000.0;
    double result = Math.round((input + BIAS) * 100.0) / 100.0;

Round according to nearest decimal value - java

3 Answers3